A common method of treating acute, recurrent, and/or chronic pain is by the topical application of heat to the afflicted area. Such heat treatments are used as a means of therapy for conditions which include aches, stiffness in muscles and joints, nerve pain, rheumatism and the like. Typically, the method for relieving pain using heat treatments has been to topically apply a relatively high heat, i. e., greater than about 40.degree. C., for a short period of time, i. e., from about twenty minutes to about one hour. These treatments include the use of whirlpools, hot towels, hydrocollators, hot water bottles, hot packs, and electric heating pads. Many of these devices employ reusable thermal packs containing, e.g., water and/or microwaveable gels. In general, most of these devices are inconvenient to use. Further, many of these thermal units or devices do not provide long lasting heat and also do not maintain a consistent temperature over long periods of time. The beneficial therapeutic effects from this administration of heat diminish after the heat source is removed.
The present inventors, however, have discovered that maintaining a sustained skin temperature of from about 32.degree. C. to about 50.degree. C., preferably from about 32.degree. C. to about 45.degree. C., more preferably from about 32.degree. C. to about 42.degree. C., most preferably from about 32.degree. C. to about 39.degree. C., still most preferably from about 32.degree. C. to about 37.degree. C. for a period of from about twenty seconds to about twenty-four hours, preferably from about twenty minutes to about twenty hours, more preferably from about four hours to about sixteen hours, most preferably from about eight hours to about twelve hours, wherein the maximum skin temperature and the length of time of maintaining the skin temperature at the maximum skin temperature may be appropriately selected by a person needing such treatment, such that the desired therapeutic benefits are achieved without any adverse events, such as skin burns which may be incurred by using a high temperature for a long period of time, substantially relieves acute, recurrent, and/or chronic pain, including skeletal, muscular, and/or referred pain, of a person having such pain.
The present inventors have further discovered that preferably maintaining a sustained skin temperature of from about 32.degree. C. to about 43.degree. C., preferably from about 32.degree. C. to about 42.degree. C., more preferably from about 32.degree. C. to about 41.degree. C., most preferably from about 32.degree. C. to about 39.degree. C., still more preferably from about 32.degree. C. to about 37.degree. C., for a time period of greater than about 1 hour, preferably greater than about 4 hours, more preferably greater than about 8 hours, even more preferably greater than about 16 hours, most preferably about 24 hours, substantially relieves acute, recurrent, and/or chronic pain, including skeletal, muscular, and/or referred pain, of a person having such pain and substantially prolongs relief even after the heat source is removed from the afflicted body part.
Disposable heat packs based on iron oxidation, such as those described in U.S. Pat. Nos. 4,366,804, 4,649,895, 5,046,479 and Re. 32,026, are known and can provide long-lasting heat. However, such devices have proven not totally satisfactory because many of these devices cannot maintain a consistent and controlled temperature and/or such thermal devices are bulky and have unsatisfactory physical dimensions which hinder their effectiveness. Specifically, such devices cannot be easily incorporated into wraps which can comfortably conform to various body contours, and hence, they deliver short duration, inconsistent, inconvenient and/or uncomfortable heat application to the body.
The present inventors have discovered that the use of thin, flexible materials and a plurality of individual heat cells spaced apart for their thermal packs improves temperature control and overcomes many of the past difficulties, but has introduced some new difficulties. Though inherently more flexible, thinner materials, when combined with a plurality of individual heat cells, can lead to difficulty retaining sufficient rigidity to maintain structural support of the heat cells, preventing unacceptable stretching of structures of the thin, flexible material during processing or use, and/or deterring easy access to the heat cell contents.
The present inventors have similarly discovered that the use of thin but overly rigid materials, and a plurality of individual heat cells spaced apart for their thermal pack, improves temperature control, alleviates unacceptable stretching of the material during processing or use, restores structural support of the heat cells, and deters easy access to the heat cell contents. However, thermal packs made of the thin but overly rigid material do not drape well around various body parts, even when heated, leading to a less than optimal comfortable application of heat to the body. That is, thermal packs made of overly rigid materials conform poorly to body locations, particularly body locations which require the material to bend and conform in three dimensions during use.
The present inventors have overcome these difficulties by developing disposable thermal packs, which possess some or all of the desired properties of both the thin, flexible materials and the thin, overly rigid materials mentioned above, comprising at least one continuous layer of a material which is sufficiently rigid in specific areas of the thermal packs, yet which softens in between such areas during use, most preferably comprising a semirigid coextruded material of polypropylene and ethylene vinyl acetate copolymer (EVA), together with a plurality of individual heat cells, having an exothermic composition, preferably comprising a specific iron oxidation chemistry and having specific physical dimensions and fill characteristics, spaced apart and fixed within or to the unified structure of the thermal pack. Active heat cells, that is, heat cells having a temperature of about 35.degree. C. or greater, preferably soften narrow portions of the continuous layer or layers of semirigid material which immediately surround the heat cells. Any remaining portions of the continuous layer or layers which surround the softened portions preferably remain more rigid. The narrow, softened portions act as hinges between the heat cells and between any remaining, cooler, more rigid portions, bending preferentially more than either the heat cells or more rigid portions. This results in thermal packs which possess sufficient rigidity to maintain structural support of the heat cells, to prevent unacceptable stretching of structures of the continuous layer or layers during processing or use, and to deter easy access to the heat cell contents, while still maintaining good overall drape characteristics when heated. The thermal packs, when incorporated into body wraps, pads, and the like, provide efficient and effective heat coverage by having excellent conformity with various body forms.
The present inventors have also discovered that it may be desirable to selectively place heat cells into positions fixed within or to the unified structure of the thermal pack, relative to each other which are sufficiently close so as to block some or all possible axes, which otherwise would have passed uninterrupted between the heat cells, through the thermal pack, or select regions thereof, to minimize or eliminate undesirable, uninterrupted fold lines, and/or to increase the structural support that the heat cell matrix imparts to the thermal pack. That is, placement of the heat cells into positions relative to each other which are sufficiently close to block some or all possible axes which would otherwise have passed uninterrupted, between the heat cells, causes the disposable thermal packs of the present invention to fold along a multiplicity of short interconnected fold lines oriented in a number of different directions relative to each other. Folding along a multiplicity of interconnected fold lines results in good overall drape characteristics.
It is therefore an object of the present invention to provide disposable thermal packs which comprise a unified, structure having at least one continuous layer, preferably of a semirigid material which has different stiffness characteristics over a range of temperatures, and a plurality of individual heat cells, which provide a controlled and sustained temperature and which reach their operating temperature range relatively quickly. The heat cells are spaced apart and fixed within or to the unified structure of the disposable thermal pack.
It is also an object of the present invention to provide thermal packs which can be easily incorporated into disposable body wraps, having good overall drapability while maintaining sufficient rigidity to maintain structural support of the heat cells, to prevent unacceptable stretching of the continuous layer or layers during processing or use, and/or deter easy access to the heat cell contents.
It is a further object of the present invention to provide thermal packs which adapt to a wide variety of body contours by possessing at least two dimensional drape characteristics across the thermal pack to provide consistent, convenient and comfortable heat application.
It is a still further object of the present invention to provide methods of treating acute, recurrent, and/or chronic pain, including skeletal, muscular, and/or referred pain, of a person having such pain, by maintaining a sustained skin temperature of from about 32.degree. C. to about 50.degree. C. for a period of time of from about twenty seconds to about twenty-four hours, preferably by maintaining a skin temperature of from about 32.degree. C. to about 43.degree. C. for a time period of greater than about 1 hour to provide prolonged relief from such pain.
These objectives and additional objectives will become readily apparent from the detailed description which follows.